Electric circuit.



No. 726,734. PATENTED APR. 28, 1903.. E. P. NORTHRUP.

ELECTRIC CIRCUIT.

APPLIUATION FILED SEPT. 27, 1901.

N0 MODEL.

afboznu h m? nunms PFTERS co. Pno'mLmm, wASHiNGTuN n IJNrrnn ra'rnsEDWIN F. NORTl-IRUP, OF BALTIMORE, MARYLAND, ASSIGNOR TO ROWLANDTELEGRAPHIC COMPANY, OF BALTIMORE, MARYLAND, A CORPORATION OF NEIVJERSEY.

ELECTRIC CIRCUIT.-

SPEGIFICATION forming part of Letters Patent No. 726,734, dated April28, 1903.

Application filed September 27, 1901. Serial No. 76,776. (No model.)

To all whom it may concern.-

Be it known that I, EDWIN F. NORTHRUP, a citizen of the United States,residing at Baltimore, in the State of Maryland, have invented certainnew and useful Improvements in Electric Circuits; and Ido hereby declarethe following to be a full, clean-and exact description of theinvention,such as will enable others skilled in the art to which it appertains toto make and use the same.

My invention relates to improvements in electric circuits, and moreespecially to telegraph or other circuits employing alternating or otherperiodically-varying electric currents I5 for the transmission ofintelligence; and the objects of my invention are, first, to preventmutual magnetic induction between such circuits and neighboring lines;second, toprevent the flow of foreign direct currents from earth throughthe main-line instruments, and in general to isolate these instrumentsfrom outside disturbing currents. I accomplish the first of theseobjects by dividing the line to be protected, preferably where it liesin more imity to another line, into sections or subcircuits, in each ofwhich at a given instant the current flows in the opposite direction tothat in an adjacent section and in this way neutralizing the inductiveeffects of one see- 0 tion by those of an adjacent section. This is donebyinserting in the line a series of transformers or their equivalentsand connecting these in the manner hereinafter described and shown. Bylocating one of these trans- 5 formers at each terminal station I amenabled also to operate the main-line instruments entirely disconnectedfrom earth, notwithstanding the intermediate line is grounded, and inthis manner to prevent the flow of foreign o currents, such astrolley-currents, on to that part of the line in which said instrumentsare connected.

In order to more fully describe my said invention, reference will be hadto the accompanying drawing, in which- A and B represent terminalstations connected by a line constructed according to my invention.

0 and 0' represent main-line receiving-relays; D and D, transmitters; E,any source of alternating or other periodically-Varying electriccurrents, preferably an alternatingcurreut dynamo, and F, F F and F" aseries of transformers.

The special form of telegraph-line which I have selected forillustrating the principle of my invention is, with the exception of thetransformer connections, fully described in ministratrix of Henry A.Rowland, for improvements in telegraphic distribution, filed July 24,1901, and serially numbered 69,523, and designated therein a .reflectedWave line. The character of the line, however, whether reflected wave,duplex, or simplex forms no part of my invention, it being applicable toall.

In applying my invention to the form of liueillustrated I preferablyconnect the ter-' minals of the dynamo-circuit to the primary of atransformer F and connect one of the terminals of the secondary of thistransformer to the main line and the other to earth. In this way theapparatus, such as the mainline receiving-relay connected in the dynamocircuit, is as far as direct currents are concerned entirelydisconnected from earth. The second section of the line comprises thesecondary of transformer F, the primary of transformer F the lineconnecting the two, and the earth. Similarly the next section comprisesthe secondary of one of its terminal transformers, the primary of theother, the line connecting the two, and the earth, and the same holdstrue relative to all of the intermediate sections. There may be as manyintermediate sections as desired and the transformers distributed at anydesired intervals, though it is preferable that the sections outside ofthe terminal stations be of even number. The terminal transformer F,however,has

'theapplication of Henrietta H. Rowland, ad-

the current in the primary of each transformer difiersapproximatelyonehnndrcd and eighty degrees in phase from that in thesecondary. The arrows indicate the directions of the currents at a giveninstant. It is, however, immaterial in which direction the current flowsinthecircnit at terminalstationB. Hence the connections with thesecondary of transformer F maybe made either direct, as shown, orcrossed, as in the case of thetransformers located along the line.Likewise it is immaterial whetherthe current in the line at station Aflows in the same or opposite direction from that in the adjacentsections; but with the intermediate sections of the line this ismaterial, since the nonmutual inductive character of the line is due tothe neutralizing effects produced by the oppositely-flowing currents inthe successive sections.

It is well known that the most obvious way of preventing mutualinduction between lines is to employ a return-wire parallel to and nearthe first, in which case the currents induced on one wire would beneutralized by those resulting from the same induction on the other.This method, however, is of value only when the wires are near eachother and equally near the disturbing, Wire. In contradislinction tothis idea my invention does not contemplate the employment of areturn-Wire or any of the various devices which have hitherto beenresorted to for the prevention of mutual induction; nor is myinventionconfined in its application to telegraph-lines alone, as the principleapplies alike to all lines carrying alternating or otherperiodically-varying currents; but

What I do claim as my invention, and desire to secure by Letters Patentof the United States, is-

1. An electric circuit for the prevention of mutual magnetic inductionbetween the same and a neighboring conductor, comprising a plurality ofsections in which current in one section flows in an opposite directionfrom that in an adjacent section, whereby the mutual magnetic effect onan adjacent conductor, of one section, is neutralized by that of anadjacent section, and a source of periodically-varying electric currentconnected to said circuit, substantially as described.

2. An electric circuit for the prevention of mutual magnetic inductionbetween the same and a neighboring conductor,said circuit comprising aplurality of sections in which the current flow is opposite in adjacentsections, the mutual magnetic inductive effect of one section beingneutralized by that of an adjacent section, transformers inducing thecurrent from one section to the next and a source of alternating orother periodic electric curreaps r rent connected to said circuit,substantially as described.

3. An electric circuit for the prevention of mutual magnetic inductionbetween the same and a neighboring cond uctor,said circuit comprisingaseries of transformers, a metallic condoctor and ground, the primary ofonetransformer being connected to the secondary of the next adjacenttransformer over said main line and the earth, by which the said circuitis divided into sections, the current flow in adjacent sections being inopposite directions, whereby the mutual magnetic inductive effect of onesection on a neighboring conductor is neutralized by that of an adjacentsection, and a source of alternating or other periodically-varyingelectric current connected to said circuit, substantially as described.

4. An electric circuit for the prevention of mutual magnetic inductionbetween the same and a neighboring conductor,said circuit comprising aplurality of grounded intermediate circuits, transformers inducingcurrents from one circuit on to the next, and terminal circuitsdisconnected from earth and inductively connected to the intermediatesections.

5. An electric circuit for the transmission of intelligence and for theprevention of mutual magnetic induction between the same and aneighboring conductor,said circuit comprising local terminal circuitsdisconnected from earth, a series of grounded circuits located betweenthe terminal circuits, and inductive means for impressing the currentsuccessively from one of said circuits on to the next.

6. An electric circuit for the transmission of intelligence and for theprevention of mutual magnetic induction between the same and aneighboring conductor,said circuit comprising local terminal circuitsdisconnected from earth, main-line apparatus located in said circuits, agrounded main-line circuit between the terminal circuits, and inductivemeans for impressing the current successively from one of said circuitson to the next.

7. An electric circuit carrying alternating or otherperiodically-varying currents for the transmission of intelligence,comprising local terminal circuits disconnected from earth, a groundedline-circuit, and transformers interposed between the terminal circuitsand the main-line circuit by which currents are induced from one circuiton to the next.

In testimony whereof I ailix my signature in presence of two witnesses.

EDWIN F. NORTI-IRUP.

Witnesses:

JOHN H. HOLT, GRAFTON L. MoGILL.

